For example, a scroll-type fluid machine that is applied as a compressor of a refrigeration circuit has fixed and movable scrolls in a housing. The fixed and movable scrolls form pressure chambers in consort with each other.
The movable scroll is caused to make an orbiting movement relative to the fixed scroll. In response to this orbiting movement, a refrigerant (working fluid) within the refrigeration circuit is drawn into the pressure chamber and compressed in the pressure chamber. The compressed refrigerant is subsequently discharged from the pressure chamber through a discharge port of the compressor toward a condenser of the refrigeration circuit.
In the refrigerant compression process, the pressure of the refrigerant in the pressure chamber becomes high, so that the movable scroll is applied with high thrust load. This thrust load acts to move the movable scroll away from the fixed scroll in its axis direction.
Such thrust load hampers the smooth orbiting movement of the movable scroll. The compressor is therefore provided with a thrust-receiving device, namely a thrust bearing, in between a support surface of the housing and the movable scroll. The scroll-type fluid machines disclosed in Unexamined Japanese Patent Application Publication Nos. 2005-248925, 2005-291151 and 2005-307949 each have a plurality of pressure-receiving pieces serving as a thrust bearing, the pieces being arranged in a circumferential direction. Each pressure-receiving piece is retained in a retention hole or groove that is formed in the support surface of the housing.
In each of the scroll-type fluid machines disclosed in the publications, it is necessary to dispose the pressure-receiving pieces parallel to the base plate of the movable scroll and to make the sliding surfaces of the pressure-receiving pieces, which come into sliding contact with the movable scroll, flush with one another for the purpose of preventing a fracture, abrasion, seizure or the like of the pressure-receiving pieces.
To that end, the bottom faces of the retention holes or grooves formed in the support wall also have to be parallel to the base plate of the movable scroll and located at the same distance from the base plate of the movable scroll.
The pressure-receiving pieces slide against the bottom faces of the retention holes or grooves as well, so that the bottom faces of the retention holes or grooves are also polished so that surface roughness is small. On the other hand, it is difficult and costly in manufacture to carry out the machining and grinding so that the bottom faces of the retention holes or grooves are located at the same distance from the base plate of the movable scroll, or in other words, so that the retention holes or grooves have a fixed depth.